Stumble in, take umbrage with someone, trade a few blows, and within about two or three exchanges, the subject itself goes out the window. Suddenly you're simply arguing about arguing. Eventually, one side gets bored, comes to its senses, or dies, and the row fizzles out: just another needless belch in the swirling online guffstorm.

But not for long, because online quarrelling is also addictive, in precisely the same way Tetris is addictive. It appeals to the "lab rat" part of your brain; the annoying, irrepressible part that adores repetitive pointlessness and would gleefully make you pop bubblewrap till Doomsday if it ever got its way. An unfortunate few, hooked on the futile thrill of online debate, devote their lives to its cause. They roam the internet, actively seeking out viewpoints they disagree with, or squat on messageboards, whining, needling, sneering, over-analysing each new proclamation - joylessly fiddling, like unhappy gorillas doomed to pick lice from one another's fur for all eternity